Abstract: Degradation of concrete in nuclear power plant (NPP) structures can be an age-related phenomena. Several research programs have been initiated by the U.S. Nuclear Regulatory Commission (NRC) to determine how aging is affecting the level of safety of operating nuclear plants. One such program is the Structural Aging (SAG) Program. The SAG Program involves the development of inspection methodologies for concrete structures in nuclear power plants. The work presented in this publication is a supplement to the SAG Program Potential environmental and aging factors that may affect durability of NPP concrete structures are identified, their degradation mechanisms noted, and symptoms of occurrence listed. Available nondestructive, destructive and testing techniques used in evaluating concrete structures are identified. The capabilities and limitations of the nondestructive testing methods are noted. Recommended testing methods for use in the detection of pertinent degradation factors are presented in the form of an application guide. The recommendations are based on literature review and practical experience in the application of the nondestructive testing methods to concrete structures.